Function separated type electrophotographic photoreceptors having a charge generating layer and a charge transporting layer have hitherto been proposed. Electrophotographic photoreceptors of this type have recently been used in not only electrophotographic copying machines but in printers using a semiconductor laser, a light-emitting diode, etc. as a light source. Accordingly, there has been a strong demand for a charge generating material having broad spectral characteristics of from the visible region to the infrared region (i.e., 400 to 800 nm).
None of the so-far proposed charge generating material has such broad spectral characteristics when used alone. Therefore, JP-B-59-32788 (the term "JP-B" as used herein means an "examined published Japanese patent application") suggests an electrophotographic photoreceptor having a charge generating layer containing at least two pigment dyestuffs different in spectral sensitivity (the pigment dyestuff whose spectral sensitivity is in the longer wavelength region is a phthalocyanine pigment).
However, when compared with conventional systems containing a single pigment, the above-described electrophotographic photoreceptor undergoes serious local reduction in sensitivity as shown in FIGS. 2 and 3. In FIG. 2, D, E, and F indicate spectral sensitivity of a perylene pigment, a phthalocyanine pigment, and a mixture thereof, respectively. In FIG. 3, G, H, and I indicate spectral sensitivity of a flavanthrone pigment, phthalocyanine pigment, and a mixture thereof, respectively. Further, a pigment dyestuff to be used in the longer wavelength region (i.e., infrared region), when used alone, generally exhibits poor electrophotographic characteristics, such as electrification properties, dark decay properties, and stability to environment and/or repeated use. If it is used as a mixture with a pigment to be used in the shorter wavelength region (i.e., visible region), it adversely affects the characteristics of the latter. As a result, the mixed pigment system also suffers from deterioration in the above-mentioned electrophotographic characteristics (electrification properties, dark decay properties, and stability to environment and/or repeated use) as compared with a single pigment system.